The multiplexing of a plurality of signals for transmission via a single transmission medium is common practice in the art. In particular for digital systems, a number of digital signals are multiplexed by assigning a predetermined proportion of the total bit rate available in the transmission medium to each of the signals that it is desired to transmit. The proportion of the available bit rate assigned to each signal is typically fixed in each system.
However, in multi-channel systems, often the bit rate required by different channels varies substantially from the bit rate required of other channels.
For example, Schmitz, U.S. Pat. No. 6,301,250, describes combining a time division multiplexed (TDM) signal into one or more “transmission capacity assigned” ATM channel(s). The input channels are assigned a fixed rate, so that if the bit stream from one channel far exceeds that of another, the system does not accommodate the difference. Further, no flow control for the different channels is provided.
Budge et al., U.S. Pat. No. 6,219,359, describes a device that adjusts the distribution of the bit rate allocation in response to differences between the indicated picture quality. However, the system described does not control the flow of data of different data types, such as for example bit streams and digital camcorders or video tape recorders, and does not provide flow control to reallocate bandwidth to throttle various channels up and down to fill up an existing transmission link.
Thus, there remains a need for a data transmission system which statistically controls the allocation of bandwidth to various transmission channels to most efficiently utilize the transmission link. Further, there remains a need for such a digital data transmission system which can accommodate a plurality of data types, such as for example bit stream and data packets and digital video data. Further, there remains a need for a system which controls the flow of data in a plurality of data channels by reducing the data flow in one channel while permitting increased data flow from another channel in response to the quantity of data to be transmitted. The present invention is directed to filling these and other needs in the art.